<h2>题目编号 : 71</h2>
<div style="color:#666;font-size:80%;">04 June 2004</div><br />
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<p>Consider the fraction, <i>n/d</i>, where <i>n</i> and <i>d</i> are positive integers. If <i>n</i><img src='images/symbol_lt.gif' width='10' height='10' alt='&lt;' border='0' style='vertical-align:middle;' /><i>d</i> and HCF(<i>n,d</i>)=1, it is called a reduced proper fraction.</p>
<p>If we list the set of reduced proper fractions for <i>d</i> <img src='images/symbol_le.gif' width='10' height='12' alt='&le;' border='0' style='vertical-align:middle;' /> 8 in ascending order of size, we get:</p>
<p style='text-align:center;font-size:8pt;'>1/8, 1/7, 1/6, 1/5, 1/4, 2/7, 1/3, 3/8, <b>2/5</b>, 3/7, 1/2, 4/7, 3/5, 5/8, 2/3, 5/7, 3/4, 4/5, 5/6, 6/7, 7/8</p>
<p>It can be seen that 2/5 is the fraction immediately to the left of 3/7.</p>
<p>By listing the set of reduced proper fractions for <i>d</i> <img src='images/symbol_le.gif' width='10' height='12' alt='&le;' border='0' style='vertical-align:middle;' /> 1,000,000 in ascending order of size, find the numerator of the fraction immediately to the left of 3/7.</p>

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